Actinomycetes of Howz Soltan Lake and their metabolite diversity in Iran

Abstract

Saline environments are largely unexplored sources for actinomycetes with the potential to produce biologically active secondary metabolites. A total of 34 actinomycete strains from water, sediments and mostly rhizosphere (82%) were collected from different sites of Howz Soltan Lake in Iran. Based on phylogenetic analysis, the isolated strains belonged to the genera Streptomyces, Nocardia and Saccharomonospora. Among the isolated actinomycetes, several strains had valuable biotechnological applications such as growth inhibition of human tumor cells. The results of cytotoxic assay revealed strain act9 having the most potent extract (19.716 ± 5.72 µg/ml) against the MDA-MB-231 human breast cancer cell. Also 38% of the strains had an antimicrobial activity against some pathogenic and nonpathogenic microorganisms. The ethyl-acetate extract of act18 showed the most antibacterial effect against Staphylococcus aureus, MRSA, and was further analyzed by GC/MS. Ar-tumerone (26.41%) and Butyl isodecyl phthalate (21.77%) were the main constituents detected in the extract.. This is the first time this compound is being detected in a prokaryote. Act18 showed the most 16s rRNA sequence similarity to Streptomyces youssoufiensis. In addition, a number of the isolates produced different enzymes including lipase, amylase, protease, gelatinase, urease and lecetinase. Also, the plant growth promoting activity of some actinomycete strains were shown. Some of the strains belonging to the genera Streptomyces and Nocardia increased the seed germination, stem length and the number of Echium leaves during the 20 days. Consequently, it was concluded that actinomycetes isolated from these saline lake habitats are potentially valuable for biotechnological applications.